【作者】 赵伟波；

【导师】 周鼎武；

【作者基本信息】 西北大学 ， 构造地质学， 2008， 硕士

【摘要】 鄂尔多斯盆地位于中国大陆中西部,是一个经过长期构造演化的多旋回沉积盆地。盆地中部地区是中生界油的主要产区,延长组为主力产油层位,且具有低孔、低渗、裂缝发育的特点。本文在前人研究基础上,结合野外观测、岩心观察、镜下观察、测井等资料及现代实验室分析技术,着重对中部地区上三叠统延长组含油层系进行了沉积特征、储层特点和裂缝的研究。中部地区储层的岩石类型以长石砂岩、长石岩屑砂岩为主;主要的成岩作用为压实作用、胶结作用、交代作用和溶蚀作用,成岩阶段处于中成岩A～B期,在此成岩阶段,砂岩裂缝较为发育,对储层储集性能的改善至关重要;储层的孔隙包括宏观孔隙、微观孔隙、混合孔隙,残余粒间孔和溶蚀粒间孔是油气赋存的主要空间;孔隙结构影响储层物性,储层物性整体较差,属于低孔、低渗储层;储层宏观非均质性较强,主要受沉积相和成岩作用两方面控制。中部地区延长组储层裂缝发育,以高角度张剪裂缝为主,裂缝走向以北东向为主,北西向次之,同时还存在一组近南北向和近东西向的裂缝,发育程度次于北东和北西向。开度值一般处于60～180μm范围内,密度在0.052条/m～0.44条/m之间,部分裂缝处于充填、半充填状态,充填物以方解石、泥质为主。裂缝的发育与盆地区域构造背景有关,从裂缝的切割关系判断,裂缝为两期形成,两期裂缝形成时的应力方向分别与盆地燕山期、喜山期的构造应力场分布一致。裂缝发育并不均一,主要受岩性、层厚和盆地基底断裂的影响。通过对裂缝物性的研究,认为裂缝对储层物性的影响主要反映在提高储层渗透率上,而作为油气储集空间的作用较小。通过水驱油实验研究,认为裂缝影响驱油效率,在注水开发中将起着重要作用。结合盆地构造演化、应力特征和有利油藏区带分析等资料,对中部地区延长组构造裂缝进行了初步预测。更多还原

【Abstract】 Ordos Basin, located in the middle-west of China, is a polycycle sedimentary basin after evolution for a long period. The central region of the basin is the main production area of Mesozoic petroleum accumulations, and Yanchang Formation characterized by low permeability, low porosity and well-developed fractures is the main pays. Based on the previous research, and with several methods such as field investigation, core observation, thin section analysis, logging data etc, features of sedimentation, reservoir and it’s fractrures of the oil bearing series of Yanchang Fm., upper triassic, in the central region of the Ordos Basin are studied deeply.Reservoir mainly consists of feldspathic sandstone, feldspathic lithic sandstone in the central region. And diagenesis of it, including compaction, cementation, metasomatism and dissolution, primarily in middle stage of diagenetic A~B, during which fissure develops easily. Different types of pores, such as macro pores, micro pores, mixed pores, intergranular remainder pores and intergranular dissolved pores, have been composing the main room of oil & gas accumulation together. The reservoir property grouped into the one with low porosity and low permeability is not good enogh entirely in this region. macro heterogeneity controled by sedimentary facies and diagenesis is obvious.Tensile fractures of high-angle develops well within the reservoir of Yanchang Fm. in the central region. The strike of them mainly extend from NE to SW, secondly from NW to SE; and a set of fractures, whose development degree inferior to the former, trend approximately from north to south and from west to east. The opening extent of all the fractures distribute from 60-180μm, the line density is between 0.052bar/m-0.44bar/m. respectively. A part of fractures is kept full-filled or semi-filled by calcite and mudstone. It is evidence that the development of fracture is in accord with regional tectonic background of the whole basin. According to the cutting relationships, all the fractures have been formed by two stage of tectonic movements: different stress directions during the forming of fractures are coincident with tectonic stress fields of Yanshanian and himalayanian. The asymmetric distribution of all fractures is mainly effected by lithology, layer thickness, basement fault. After fracures studied, it is proved that the effect of fracture toward reservoir mainly on improving permeability of reservoir, secondly on enlarging the accumulation. On the basis of oil-water displacement experiment, it is thought that fractures have effect on oil displacement efficiency and play an improtant role on waterflooding. Based on the data about tectonic evolution of the basin, stress feature, and favorable zone of oil reservoir together, tectonic fracture was preliminarily predicted.更多还原